This invention relates to apparatus for winding strips of material into coils, and more particularly to a recoiling drum incorporating gripping means for gripping the end of the strip to be coiled, and also means to selectively vary the circumference of the drum while the drum is rotating.
In many instances when a sheet of metal supplied in roll form is desired to be cut into a plurality of narrower strips which are to be rewound in coil form, the recoiling operation frequently results in problems because the original sheet is not of uniform thickness across its width. Oftentimes the sheet is thicker at its center than it is at its edges. As a consequence when such a sheet is slit into narrower strips and tension is applied in order to provide tightly wound coils, those strips at the center of the sheet are wound more tightly on the recoiler or take-up roll and also more quickly because the additional thickness results in a larger diameter coil, the tangential velocity of which is greater than that of the outer coils. Thus those strips toward the edges of the sheet are wound with lower tension, causing looser coils and also causing sagging of the outermost strips between the slitter and the recoiling drum, which results in the strips dragging on and accumulating on the factory floor between the slitter and recoiler.
Several methods have been devised to overcome the above-mentioned problems, one of which involves providing a so-called looping pit to permit the outermost strips to extend into a substantially rectangular depression positioned between the slitter and the recoiler and below the floor level. Oftentimes pits of this type have a depth of perhaps ten (10) feet or so. An example of such an arrangement utilizing a looping pit to receive slack strips is shown in U.S. Pat. No. 3,672,595.
Another method suggested to overcome the problems mentioned above involves positioning spacers in the outermost coils as they are being wound, in order to increase their diameter and thereby to increase the take-up velocity, which, in turn, reduces the sag in the outermost strips. For example, in U.S. Pat. No. 4,093,141 there is shown a device for intermittently shooting fibreboard spacers between a slit web and the coil around which it is being wound.
Still another way in which coil looseness and strip sagging problems have been addressed is to permit circumferential slippage of certain of the coils as they are being wound upon the recoiling drum. In that type of arrangement the innermost coils would be permitted to slip with respect to the drum so that the take-up velocity of the innermost strips is reduced to approximately that of the outermost strips, thereby permitting the recoiler to be driven at such a speed that sagging and loose coils are avoided. Such a method is disclosed in U.S. Pat. No. 4,093,140, together with one form of apparatus intended to permit practicing that method. Another form of apparatus for practicing that method is shown in U.S. Pat. No. 4,199,116. Another patent which shows a similar method but which also includes the interposition of means to connect a portion of each strip to a previously wound portion of the same strip is U.S. Pat. No. 4,201,352.
In the apparatus described in connection with the slip-coil methods of tension equalization disclosed in the above-identified patents, the recoiler drum is collapsible to a certain extent, to permit the slippage of the innermost coils to take place, and the means by which the leading edges of the respective strips are initially gripped is releasable. However, the structural arrangement disclosed in U.S. Pat. No. 4,199,116 is not capable of re-expanding a collapsed drum while the drum is rotating, a feature which is highly desirable for greater flexibility of operation. Although the apparatus disclosed in U.S. Pat. No. 4,201,352 may be capable of such operation, it utilizes a flexible hose member which can be expanded or contracted by the addition or removal of hydraulic fluid. Such an arrangement is subject to leaks of hydraulic fluid and possible hose breakage.
It is an object of the present invention to overcome the deficiencies of the prior art devices and to provide an improved recoiling drum which includes positive means to grip the strips of material being wound on the drum, and also to provide mechanical means for positively releasing the gripper engagement while simultaneously reducing the effective drum diameter and subsequently permitting reclosing of the gripper device and also re-expansion of the drum, as desired, with any number of subsequent opening and closing operations as may be necessary during a particular recoiling operation.